Increased options and flexibility in common rail direct injection provides a great opportunity for combustion optimization using fuel and air system with proper combustion chamber configuration. This paper elaborates the experimental work conducted for combustion optimization with combinations of piston bowl, intake port swirl, injector specifications and turbo charging on a 3.8 l four valve diesel engine of LDT application equipped with common rail fuel injection system and waste gate turbo charge. In meeting the target emission norms with internal engine measures, the design of the piston bowl and the nozzle configuration perform a defining role. Through simulations the best option had been carried out parametrically investigate the influence of piston bowl geometry and nozzle characteristics on the performance of the combustion system. Then experimental tests were carried out with Design of Experiment (DoE) method applied to analyze a matrix of piston bowls with parametric variations in geometry. Further, the influence of the nozzle cone angle, hydraulic flow rate, number of holes and their combination were determined using systematic parameter variations with selected piston bowl designs. The performance of the various hardware configurations were evaluated based on the exhaust emissions and fuel consumption values.The tests were carried out to understand best combination of air and fuel system along with major design related variables to achieve best combustion for emission, performance and BSFC.